按照 ruby-china 的代码

def render_optional_error_file(status_code)
    status = status_code.to_s
    if ["404","403", "422", "500"].include?(status)
      render :template => "/errors/#{status}", :format => [:html], :handler => [:erb], :status => status, :layout => "application"
    else
      render :template => "/errors/unknown", :format => [:html], :handler => [:erb], :status => status, :layout => "application"
    end

好像拦不住的